I’m in the Boston area. They’re listed as beef sweetbreads (not veal or lamb, anything fancy). It’s packaged, so it’s not from a local butchery and I’ve never seen them sold before. The price is definitely crazy low, even with nothing to compare it to. This is a local store of a regional chain and this location is selling more different cuts of meat, probably because there is a surging Asian population in the area, and in general the increase interest in offal and non-standard cuts. You usually see gizzards, various bones including marrow bones, and even chicken feet in this market. Someone either made a serious mistake in the pricing, or they are trying to move this product that isn’t selling so hot.
